Geometrical device



Jan. 18, G- B-. STEWART GEQMETRICAL DEVICE Filed Mav 26, 1926 INVENTOR GEORGEBST'EWG RT.

Patented Jan. 18, 1927.

UNITED STATES PATENT OFFICE.

enomn'raroar. nnvrcn.

Application filed May 26,

This invention relates to improvements in geometrical devices and more particularly to lmprovements in stencils for geometrical designs and the objects of the invention are I! to provide a device of this description for use in schools whereby knowledge of geometry maybe more readily and expeditiously imparted to pupils and whereby the work of students studying modern geometry may be simplified and rendered attractive.

With these and other objects, hereinafter more fully referred to in view, the invention consists essentially of an improved stencil for geometrical designs such as congruent triangles or polygons, similar triangles or I polygons, regular hexagons, pentagons or octagons, angles of different degrees, circles, squares, parallelograms etc., for proving the theorems used in modern geometry.

Referring to the drawing in which like characters of reference indicate corresponding arts,

T e figure is a plan view of a preferred example of my improved stencil constructed of any suitable material and consisting of a sheet of transparent material, such as celluloid, in which are cut out a plurality of geometrical designs-including circles 11 and 12, of diiferent circumferences, a rhomboid 13, a right-angled triangle 14, an equilateral triangle 15, acute-angled triangles 16 and 17 and an obtuse-angled triangle 18. A T- square is also cut out. p

The circles 11 and 12 are marked on the edges, as at 20, in degrees to enable pentagons 22, hexagons 23 and octagons 24 to be drawn as indicated in dotted lines.

Furthermore, in the stencil are preforations, as at 24 and 25, to enable, in combination with the corners 26 and 27 of the rightangled triangle 14, a square 28 to be drawn as indicated by dotted lines, the other corner 29 and the corner 27 cooperating with perforations 30 and31 to enable a square 32, as indicated by dotted lines 33, to be drawn.

Further perforations 34' and 35 enable, in combination with the corners 29 and 26 of the right-angled triangle 13, a smaller square 36 to be drawn as indicated by dotted lines.

The sides 37 and 38 of the sheet 10 are preferably marked with a scale made in inches and centimetres, respectively, while adjacent the side 39 are spaced orifices to grliable the sheet to engage with a loose lea'f e. From the foregoing it will be seen that in order to draw congruent triangles or polyfigure for the Pythagorean theorem, parallel 1926. Serial No. 111,83l).

gons the pupil will only have to place the stencil on a. sheet of paper and trace with a pencil a triangle in duplicate or join the points of a polygon marked in the circle 11 or 12. To draw similar triangles it is only necessary for the pupil to follow the outlines of the acute-angled triangles 16 and 17 and to draw circles only necessary to follow the outline of the circle 11 or 12. The drawing of squares and parallelograms has already been disclosed. .Rectangles are drawn by using the rhomboid 13 and so on. In addition to this the pupilis enabled to draw the lines, lines at right angles to each other, (with the T-square), inscribe a triangle within a circle, circumscribe a circle about a tria gle, measure in inches (by the side 37 and i centimetres (by the slde 38), thus materially simplying the work of students in the study of modern geometry.

Furthermore, as is well'known, without a device of this kind it would be impossible for a student, without considerable trouble, to draw two exactly similar triangles while with the device it is quite simple.

As many changes could be made in the above construction and many apparently widely difi'erent embodiments of m invention, within the scope of the claim, constructed without departin from the spirit and scope thereof, it is intended that all matter contained in the present s ecification and accompanying drawings shal be interpreted in an illustrative and not in a limiting sense.

What I claim as my invention is:

A stencil comprismg a sheet of transparent material having scales marked thereon, the body of the sheetbeing cut out in a pluralit of sections to form circles of different iameters, congruent and similar triangles, a T-square and a rhomboid, there being perforations in the sheet designed to 100 cooperate with the corners of one of the triangles to outline squares onthe respective sides thereof, preferably a right-angled triangle, to enable squares, parallelograms, and rectangles to be drawn, there being mark- 105 ings on the edges of the cutout circles whereby, on certain indicated markings being connected, entagons, hexagons and octagons may be rawn.

h Ini witness whereof I have hereunto set my 11.

GEORGE BENJAMIN STEWART. 

